1. Field of the Invention
The present invention relates to a sound deadening member for electrophotographic photoreceptor having an excellent vibration damping property, a high rigidity, a shock resistance, and a good working balance and to an electrophotographic photoreceptor using it.
2. Description of the Related Art
Recently, the tendency of requiring a comfortability of the living environment becomes active and vibration damping and the reduction of noise from instruments in the living environment have been required. Particularly, in office instruments, domestic electrical appliances, sound instruments, etc., higher tone qualities have been required. Also, because from the change of a mode of life, domestic electrical appliances such as refrigerators, washing machines, cleaners, etc., become large-sized, whereby the vibrations and noises generated by these electric appliances become large, in these products, the quietness by low vibration and low noise becomes one of the important performances of the commodities.
In these products, in the office instruments such as copying machines, printers, etc., the reduction of noises and vibrations generated from these instruments has become an important problem for keeping a good work and good living environment. In these office instruments, because in particularly a photoreceptor portion which is the printing portion of an electrophotography such as an electrophotographic copying machine and printer, etc., a high frequency giving the most unpleasant feeling to human beings is liable to generate from the mechanism thereof, as the counterplan therefor, a sound deadening part is formed and various investigations have been made about the structure, etc.
That is, as shown in FIG. 1, the photoreceptor of a copying machine is constituted of a photoreceptor drum 1 having a photosensitive layer formed by coating a photosensitive material on the surface of a pipe made of iron, aluminum, etc., and having a plain surface for keeping the uniformity as the photoreceptor, and the photosensitive layer is electrostatically charged by applying thereto a direct current or an alternating current, or a direct current and an alternating current by an electrostatically charging device 2 and printing is carried out. The charging device 2 has the construction that an elastic layer made of a urethane rubber, a styrene-butadiene rubber, an ethylene-butadiene rubber, a nitrile rubber, or a mixture thereof is formed on the outside of a core material made of iron, aluminum, etc., and the elastic layer may be a single layer or plural layers. The alternating current applied by the charging device 2 is desirably from 1.5 to 1.6 kV but may be from 1.0 to 2.0 kV. The frequency of the applying alternating current depends upon the rotation speeds of the charging device 2 and the photoreceptor drum 1.
At printing, by the charging device 2, a vibration is given to the photoreceptor drum 1 according to the frequency in the case of applying an alternating current, whereby the photoreceptor drum 1 generates a noise. The noise becomes a large vibration of the applied frequency or an integer times thereof, and particularly, the frequency of from 1000 to 3000 Hz is perceived as a jarring sound. Thus, a sound deadening member 3 is fixed to the inside wall of the photoreceptor drum 1 for the noise prevention. In order that the sound deadening member 3 is easily inserted in the inside of the photoreceptor drum 1 and is easily released therefrom, and also is closely fixed to the inside wall surface of the photoreceptor drum 1, in the sound deadening member 3, a cut portion 3A of at least 0.5 mm is formed at one portion of the cylindrical cross section and a hinge portion 3B having a thickness of not thicker than 1/2 of the general thickness of the sound deadening member 3 is formed, and the outside diameter of the sound deadening member 3 is the diameter that when the sound deadening member 3 is fixed to the inside wall surface of the photoreceptor drum 1, all the outside portions of the sound deadening member 3 is brought into contact with the inside wall surface of the photoreceptor drum without forming a gap.
Also, vibration damping resin members suitable for vibration damping of the metal portion of the sound deadening part have been investigated and a resin having sufficient vibration damping property, rigidity and shock resistance, and being suitable for the recycling property of considering the environmental problem in the recent increasing environmental consciousness has been required.
Under these circumstances, styrene-base resins such as, typically, a PS resin, an AS resin (or an SAN resin), an HIPS resin, an ABS resin, an AAS resin, an AES resin, etc., are excellent in the moldability, the shock resistance, the appearance, the weather resistance, etc., and have been widely used for the above-described products, etc., while selecting each resin according to the necessary characteristics. However, these resins are poor in the vibration damping performance, whereby lowering the vibration and the noises cannot be sufficiently attained, and thus, the improvement of the point has been earnestly desired.
On the other hand, as plastics having a high vibration damping performance, polyolefin-base resins are known but because these resins cause a warp at molding and show a large molding shrinkage, there is a problem that these resins are unsuitable for the use requiring a high dimensional accuracy, such as office instruments, etc. As the counterplan for the point of the dimensional accuracy, materials compounded with an inorganic filler have been investigated but there is a problem that by compounding of an inorganic filler, the vibration damping performance is deteriorated.
Also, as a vibration insulator and a vibration damper, it is desirable that the structure itself has a vibration decaying property but because a material having a high rigidity, such as a styrene-base resin which can generally become a structural body and a material having a large vibration damping factor, such as a rubber composition such as, typically, a rubber vibration insulator are in the relation of antinomy that the former has a small vibration damping factor, while the latter has a low rigidity, it is difficult to use a resin composition having a vibration damping performance as a structural body.
As the counterplan thereof, Japanese Patent Laid-Open No. 41443/1994 proposes a mixture of a copolymer having a glass transition point of at least 0.degree. C. made of an acrylic acid ester monomer and/or a methacrylic acid ester monomer and other monomer and other thermoplastic resin. In the proposed invention, because the resin composition contains an acrylic acid ester-base copolymer having a relatively low glass transition point, a property very near a rubber is imparted to the resin composition in a room temperature environment and as the result thereof, a vibration damping property is realized. Accordingly, in the resin composition, under a high-temperature environment, a vibration damping property is obtained to a certain extent but at a temperature near room temperature and a low-temperature region, the vibration damping property and other properties are insufficient, and a stable vibration damping performance cannot be obtained in a wide frequency region, such as particularly, the vibration damping property at a high frequency region of giving unpleasant feeling to human beings is inferior. Therefore, the resin composition is not for practical use and is particularly unsuitable for a sound deadening member for an electrophotographic photoreceptor wherein the vibration damping property in a high frequency region is regarded to be important.